Method for weighting artificial silk consisting of cellulose esters



Patented, Apr. 25, 1933 UNITED STATES PATENT OFFICE FRIEDRICH W'ILHIILM WEBER, OF HACKENSACK, AND EUGENE SCHAEFER, OF ENGLE- WOOD, NEW JERSEY, ASSIGNORS TO MLAYWOOD CHEMICAL WORKS, 015 MAYWOOD, NEW JERSEY, A CORPORATION OF NEW JERSEY METHOD FOR WEIGIEI'I'ING ARTIFICIAL SILK CONSIS'IING OF GELLULOSE ESTEBS No Drawing.

The present invention'relates to a method for weighting artificial silk consisting .of cellulose esters as they are now brought on the market under various trade-names, the

object of the invention being to provide a method by which it is possible to weight such artificial silk similarly as is done with natural silk since long.

Artificial silk is relatively low in weight and garments made from such artificial silk hang loosely on the body and are, therefore, not of such attractivenappearance as one would expect on account of the silk-like properties of the artificialsilk.

Efforts were made by the silk dyers to accomplish the weighting of artificial silk by the same processes as applied in the weighting of natural silk, but it has been found impossible to weight artificial silk in the manner adopted for natural silk, in which the weighting often amounts to several hundred percent of the fiber. In so far as proposals'for this purpose exist, they are confined to weighting artificial silk up to approximately 5 per cent.

One of us, Friedrich W. Weber, has described in his copending application, Serial No. 25,707, filed February 3, 1930, the weighting of both natural and artificial silks of all kinds with insoluble compounds. -of tin and of rare earth metals, while both of us have described in our copending application, Serial No. 515,138, filed February 11, 1931, a method of weighting both natural and artificial silks of all kinds with insoluble tin compounds and such; of metals other than a rare earth metal, the chloride of which is soluble in water and the phosphate ,of which is insoluble therein; the method of our application also allows to combine the insoluble compounds of the rare earth metals with those of other metals.

In our aforesaid application Serial No. 515,138 we have shown that both natural and artificial silk may successfully be weighted with a solution, made by dissolving the carbonate of a metal, forming a soluble chloride and an insoluble phosphate, in the solution of a salt of a weighting metal, such as tin, by subjecting the silk first to the afore- Application filed July 3, 1931. Serial No. 548,708.

said de-acidified solution and then subjecting the silk to the solution of a salt forming an insoluble salt with the metal, such as tin.

We also have shown in aforesaid application Serial N 0. 515,138 that the salt solution of the weighting metal, such as tin, may be de-aeidified with the mixture of the carbonate of a rare earth metal and that of another metal, forming a soluble chloride and an insoluble phosphate; and we have, furthermore, shown in said application that for the de-acidification of this weighting metal salt solution, such as tin-tetrachloride solution, we are not restricted to the carbonate form of the metals, but that any other form of their basic compounds, such as their hydroxides and the like may be applied with like success, but that also certain salts, in which the metal oxides display an acid character, for instance, sodium zincate, sodium plumbate, sodium aluminate, sodium stannate, etc. may be applied with good success. \Ve also pointed out that if natural or artificial silk is to be dyed in dark shades, insoluble metal salts of dark colors are very desirable in the weighting of the silk, as a pretreatment for or part of the dyeing process.

While our investigations have shown that in both natural and artificial silks deposits of substantial amounts of insoluble compounds of tinand of other metals can be brought about so that in each case -a considerable weighting has taken place, which goes far beyond what was possible in the prior art, we have also noticed that the various kinds of artificial silk take rather differently to the weighting materials.

The present invention is based on aforesaid observation and relates particularly to the weighting of artificial silks which are esters of cellulose, for instance cellulose acetate and cellulose for-mate. Cellulose nitrate silk belongs also to this class of compounds, but today all silk made from cellulose nitrate is de-nitrated, to deprive it of its explosive character, and as such silk is then practically cellulose, probably partly hydrocellulose, cellulose nitrate has only a theoretical relation to the subject matter of the present application.

As compared with the other artificial silks, which are known as cuprammonium silk, viscose silk, collodion silk, the mostly used ester silk, cellulose acetate, occupies a special position. Its resistance to water and its very slight powers of gelatinizing in that medium, in themselves cause considerable inertness towards chemicals, such as dyestuffs, weighting materials, so that the difficulties appeared almost unsurmountable. We have succeeded, however, in finding special materials and methods and in making these observations we found that the cellulose ester silks, particularly cellulose acetate, display a peculiar selective property against certain chemicals as compared with that of other artificial silks, such as viscose silk, cuprammonium silk, etc.

While the cellulose ester silks fully answer the requirements of the method described in the aforesaid applications, Serial Nos. 425,707 and 515,188, we found that they display a rather surprising preferance for zinc compounds in combination with tin compounds. On the ground of this observation we have succeeded in establishing a precise and promptly acting method for the weighting of artificial silk consisting of cellulose ester silks and to obtain-products of considerable increase in weight, elasticity, strength and great luster.

For the better understanding of our invention, we shall describe how we may proceed to carry the same into effect and we choose cellulose acetate as the kind of ester silk for this description of our method given in the example below.

Example 750 grams of a solution of tin-tetrachloride of 50 B. is heated to approximately C. and then 100 gr. zinc carbonate are entered into the same; the carbonate dissolves and the solution is then diluted with water to one (1) liter.

The solution thus obtained is practically colorless, absolutely clear and is, therefore, well suitable for weighting purposes. We found that we can weight with it equally well cellulose acetate silk in skeins or in the form of any kind of fabric, that the solution can be used over and over again without any regeneration or adjustment, and that the goods after each immersion show practically the same increase in weight, particularly if we proceed in the following manner:

The weighted cellulose acetate is soaked for 1-2 hours in the solution while the same is occasionally agitated. Thereupon the goods are taken out, the surplus of solution is removed mechanically in any of the well known ways, they are then washed with water and are then introduced into the solution of an alkali-metal phc'nhate, silicate, tungstate,

molybdenate, such as di-sodium phosphate,-

or sodium silicate, respectively, etc. includ-v ing also the corresponding ammonium salts in the group of aforesaid salts.

If we, for instance pass the goods thus treated into a di-sodium phosphate solution to fix the tin and zinc in the form of their phosphates on the silk, we find that the goods, well washed and dried after each passage through the sodium phosphate, show an increase in weight of 21% after the first, of 37% after the second and of 60% after the third passage. This is the usual number of passages given to the artificial silk and it is self-evident that by further passages of the artificial silk, such as celanese, the weight will still increase.

In connection with the above facts it appears of importance to state that in the prior art of silk weighting, the skeins of silk, after they were soaked for sometime in a tin-tetrachloride solution were deprived as much as possible of the surplus of the same before the goods were washed with water. This was preferably done by centrifuging the wet skeins, and the reason for this operation was the wish to avoid the loss of the adhering tin-tetrachloride because when the washing was done unnecessarily much tintetrachloride was lost in the Washing water, from which it could hardly profitably be recovered. Furthermore, the excess of the adhering tetrachloride would unduly delay or extend the time required for completing the hydrolysis of the tin-tetrachloride actually kept in the fiber.

In our new process, however, the de-acidified tin-tetrachloride offers much more favorable conditions because we apply a solution in which the salt is already contained in a basic form, which is inclined to complete its hydrolysis more readily so that after the soaking of the fibers it is not absolutely necessary to remove the excess of the basic tin-tetrachloride.

What we claim is:

l. The method for weighting artificial silk formed by an ester of cellulose, said method consisting in acting on the artificial silk with a solution containing basic chlorides of tin and zinc, then washing the artificial silk with water, and subjecting the artificial silk thus treated with the solution of a salt capableof forming insoluble salts with tin and ZlIlC.

2. The method of weighting artificial silk formed by an ester of cellulose, said method consisting in acting with zinc carbonate upon tin-tetrachloride solutions thereby producing a clear solution of basic tin-zinc chlorides, acting with the aforesaid clear solution upon the artificial silk, and then acting upon the same with the solution of di-sodium phosphate.

,3. The method of weighting celluloseacetate silk, said method consisting in acting with zinc carbonate upon tin-tetrachloride solution thereby producing a clear solution of basic tin-zinc chlorides, acting with the aforesaid clear solution upon the cellulose acetate silk, and then acting upon the same with the solution of di-sodium phos phate.

In witness whereof we have hereunto set 10 our hands.

FRIEDRICH WILHELM WEBER.

EUGENE SCHAEFER. 

